system to fall apart. For this reason, the security of hash functions is

essential to the security of the blockchain.

The security of the hash function can be threatened in the following few

different ways:

Algorithm strength: Hash functions are designed to be collision-

resistant, but cryptographic algorithms are occasionally broken. If a

flaw is discovered in a hash function, it may make it possible to

effectively find hash collisions.

Hash output length: Hash functions are designed to make the best

way to find a collision a brute force search, with the search space

equal in size to the space of possible outputs of the hash function. If

such a space becomes effectively searchable—

due to the use of a hash

function with too short of an output length—

then the hash function is

no longer collision-resistant and is vulnerable to attack.

Quantum computing: Grover’s algorithm is an algorithm that

reduces the space that an attacker needs to search to find a hash

collision designed for quantum computers. With quantum computers,

this may enable collisions to be found for hash functions that were still

secure against attacks by classical computers.

In conclusion, since the ledger is stored in a decentralized fashion, with

each node maintaining its own copy, ledger immutability is critical.

Otherwise, nodes could change their versions of the ledger to their own

benefit, breaking the network’s consensus.

This makes hash function security vital to blockchain security. If a

blockchain’s hash function becomes vulnerable to attack, then the security

of the entire system is broken.

Types of hash functions are explained as follows:

1. Secure hashing algorithm (SHA-2 and SHA-3)

The most famous of all cryptographic hash functions is SHA-25 6

because it is used extensively in blockchain technology. The National

Security Agency (NSA) in 2001 developed the SHA-25 6 hashing

algorithm.

Hashing process: